Ultra-seal gasket for joining high purity fluid pathways

ABSTRACT

A ring-shaped gasket for making high-purity fluid pathway connections between opposing fluid delivery apparatus elements having at least one simple flat surface in contact with the gasket. The face of at least one apparatus element typically has a circular counterbore depression to receive the gasket, but is not required. The gasket has a body, pierced through by a hole creating a fluid pathway and defining a radial inner surface, and additionally having a radial outer surface, a first axial end surface and a second axial end surface. At least one of the first and second axial end surfaces has a stress concentration feature radially adjacent to a gasket sealing region, the sealing region constructed to be in contact with a face surface of a corresponding fluid conduit port. The stress concentration feature may be a groove or a plurality of cavities disposed adjacent the gasket axial end surface sealing region.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application Ser. No. 61/980,823 titled “ULTRA-SEAL GASKETFOR JOINING HIGH PURITY FLUID PATHWAYS,” filed Apr. 17, 2014, which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Embodiments of the present invention are related to malleable, primarilymetallic, gaskets for sealing joints between portions of a fluidpathway. Many combinations of interface structures and associatedgaskets are well known in the design of fluid delivery apparatus. Thesestructures include flanges, glands, component connections, and otherfunctions that enable mechanical assembly of various apparatus elementsforming a collection of interconnected fluid pathways. Representativefluid delivery apparatus are found among industrial equipment producingfine chemicals, petroleum products, flat panel electronic displays, orsemiconductors, and may be subjected to vacuum, or pressure, or purityrequirements, and combinations thereof. Fluid pathways among elementsintended for manipulating process materials within semiconductormanufacturing equipment usually require attention to maintaining highpurity of the delivered reactants and also typically have a much smallercross-section than fluid pathways used in petrochemical plants, forexample. In many cases practitioners have found metallic gaskets providesuperior performance, particularly regarding diffusion of process fluidor contaminants through the gasket and consequent resistance toundesirable leakage, in preference over polymer materials.

One known type of fluid pathway joint uses a ring-shaped gasket,initially flat in a radial direction, axially compressed betweennominally identical shaped annular projections that surround circularconduit openings of opposing apparatus elements. The annular projectionsare urged axially toward each other causing permanent plasticdeformation of the ductile metallic gasket creating a seal that willresist leakage of even difficult to contain fluids such as helium.Representative examples of such joints may be seen in U.S. Pat. No.3,208,758 issued to Carlson and Wheeler (familiarly known as the Varian®Conflat® flange), in U.S. Pat. No. 3,521,910 issued to Callahan andWennerstrom (familiarly known as the Swagelok® VCR® fitting), and inU.S. Pat. No. 4,303,251 issued to Harra and Nystrom.

Another known type of fluid pathway joint uses a ring-shaped gasket ofpredetermined cross sectional profile compressed between nominallyidentical shaped annular projections that surround circular conduitopenings of opposing apparatus elements. Representative examples of suchjoints may be seen in U.S. Pat. No. 4,854,597 issued to Leigh, in U.S.Pat. No. 5,505,464 issued to McGarvey, and in U.S. Pat. No. 6,135,155issued to Ohmi et al. (an early version of the W-Seal joint type). Thepatent to Ohmi et al. additionally provides a separate retainer meansfor holding and centering the gasket during joint assembly. Otherseparate retainer structures may also be seen in U.S. Pat. Nos.5,673,946 and 5,758,910 both issued to Barber and Aldridge, and in U.S.Pat. No. 7,140,647 issued to Ohmi et al.

Yet another known type of fluid pathway joint (familiarly known as theC-Seal joint type) uses a ring-shaped metallic gasket of complex shapecompressed between opposing apparatus elements having simple flatsurfaces in contact with the gasket. Most usually the face of at leastone apparatus element has a circular counterbore depression to receivethe gasket. Representative examples of such joints may be seen in U.S.Pat. No. 5,797,604 issued to Inagaki et al., in U.S. Pat. Nos. 6,357,760and 6,688,608 both issued to Doyle, and in U.S. Pat. No. 6,409,180issued to Spence & Felber. The '180 patent issued to Spence and Felberadditionally provides a separate retainer means for holding andcentering the gasket during joint assembly. Other separate retainerstructures may also be seen in U.S. Pat. No. 5,984,318 issued to Kojimaand Aoyama, in U.S. Pat. No. 6,845,984 issued to Doyle, and in U.S. Pat.No. 6,945,539 issued to Whitlow et al. Additionally, U.S. Pat. No.5,992,463 issued to the present inventor Kim Ngoc Vu et al, and U.S.Pat. No. 5,730,448 issued to Swensen et al., show a suitably thickretainer may instead provide the compression limiting function of acounterbore sidewall and allow use of a gasket between simple flatopposing faces.

High purity fluid delivery components and fluid pathway elements areoften made from a vacuum refined variation of type 316L stainless steelor nickel alloys such as Hastelloy® C-22®. Both of those metallicmaterials can only be hardened by mechanical work rather than heattreatments and consequently are at risk of being damaged by thelocalized forces accompanying metallic gaskets. High purity fluiddelivery components made from polymer materials are also well known andoften used when controlling flow of certain liquid fluids wherepotential contamination with metallic ions is a concern. In many polymerapparatus designs, fluid pathway joints also use opposed flat surfaces(with or without counterbores) with an interposed gasket. Gaskets madefrom polymer materials for use in such joints may also benefit from theinventive designs described in this disclosure.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to a ring-shapedgasket for sealingly joining opposed fluid conduit ports. The fluidconduit ports may correspond to adjacent fluid conduit ports of a fluiddelivery system, such as a semiconductor gas panel, a petrochemicalproduction or distribution system, etc. The gasket has a body, piercedthrough by a hole creating a fluid pathway and defining a radial innersurface, and additionally having a radial outer surface, a first axialend surface and a second axial end surface. At least one of the firstand second axial end surfaces has a stress concentration featureradially adjacent to a gasket sealing region, the gasket sealing regionconstructed and arranged to be in contact with a face surface of acorresponding fluid conduit port. In one embodiment, the stressconcentration feature defines a lip in the gasket sealing region thatincludes a protective ridge and a sealing surface. Prior to jointassembly the sealing region lip desirably projects axially outwardbeyond the corresponding axial end surface.

In an embodiment the stress concentration feature comprises a groove ineither one or both of the axial end surfaces and adjacent the one orboth corresponding gasket sealing regions. In another embodiment thestress concentration groove undercuts one or both sealing regions. Insome embodiments, the stress concentration groove has a V-shapeundercutting one or both sealing regions, and in other embodiments, thestress concentration groove has a U-shape with substantially parallelsides undercutting one, or both sealing regions.

In yet another embodiment the stress concentration feature comprises aregular arrangement of blind cavities projecting into either one or bothof the axial end surfaces. In another embodiment the regularly arrangedstress concentrating blind cavities undercut a one or both sealingregion lips. In another embodiment the circumferential phaserelationship of the blind cavities may be coincident or interposed inanti-phase.

In yet another embodiment a first axial end surface has a stressconcentration feature that includes a regular arrangement of blindcavities undercutting a first sealing region and a second axial endsurface has a second sealing region initially flat in a radialdirection. In another embodiment a first axial end surface has a stressconcentration feature including a groove undercutting a first sealingregion and a second axial end surface has a second sealing regioninitially flat in a radial direction. The groove may have a V-shape, ora U-shape with substantially parallel sides. In any embodiment eitherone or both of the axial end surfaces may have a circumferential regionadjacent the gasket radial outer surface which serves as a stop to limitcompression of the deformable sealing region.

The ring-shaped gasket of the various embodiments described herein maybe formed of a malleable material. The malleable material can include aunitary metallic material selected from the group consisting of astainless steel alloy, a chromium alloy, a nickel alloy, commerciallypure nickel, a copper alloy, and commercially pure copper, a unitarymetallic material substantially identical to type 316 series stainlesssteel alloy, a unitary polymer material selected from the groupconsisting of polypropylene (PP), polyvinylidene fluoride (PVDF),perfluoroalkoxy polymer (PFA), polytetrafluoroethylene (PTFE),polychlorotrifluoroethylene (PCTFE), and polyimide, or a unitary polymermaterial substantially identical to polyimide.

In accordance with various aspects described herein, a method of forminga high purity fluid joint is provided wherein a gasket, starting as aclosed loop of malleable material having an undeformed gasket sealingsurface angled athwart a proximal interior axis of the gasket loopshape, is compressed between opposing fluid delivery apparatus elementsuntil a portion of the gasket sealing surface is bent substantiallyperpendicular to the proximal interior axis of the gasket loop shape.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1A is a first representative gasket sectioned on a diameter;

FIG. 1B is an enlarged cross-section of the first representative gasketshown in FIG. 1A;

FIG. 2A is a second representative gasket sectioned on a diameter;

FIG. 2B is an enlarged cross-section of the second representative gasketshown in FIG. 2A;

FIG. 3A is a third representative gasket sectioned on a diameter;

FIG. 3B is an enlarged cross-section of the third representative gasketshown in FIG. 3A;

FIG. 3C is the third representative gasket of FIG. 3A shown inperspective view;

FIG. 4A is a fourth representative gasket sectioned on a diameter;

FIG. 4B is an enlarged cross-section of the fourth representativegasket;

FIG. 5A is a fifth representative gasket sectioned at two locations;

FIG. 5B a plan view of the fifth representative gasket showing the notdiametric (anti-phase) relationship of the two sectioning locations;

FIG. 6A illustrates the fourth representative gasket located by a keeperand positioned within fluid conduit port counterbores prior to theapplication of axial sealing force to make the joint;

FIG. 6B illustrates the fourth representative gasket in fluid conduitport counterbores after the joint has been made;

FIG. 7A is a sixth representative gasket sectioned on a diameter;

FIG. 7B is an enlarged cross-section of the sixth representative gasketshown in FIG. 7A;

FIG. 7C is an enlarged cross-section of an alternative example of thesixth representative gasket in which the stress concentration feature onthe first axial end surface of the gasket includes a stressconcentration groove;

FIG. 8A illustrates the sixth representative gasket located by a keeperand positioned between a fluid conduit port counterbore having a flatbottom and a fluid conduit port counterbore having a shaped annularprojection prior to application of axial sealing force to make thejoint;

FIG. 8B illustrates the sixth representative gasket betweencorresponding fluid conduit port counterbores after the joint has beenmade;

FIG. 9A is a seventh representative gasket sectioned on a diameter;

FIG. 9B is an enlarged cross-section of the seventh representativegasket shown in FIG. 9A;

FIG. 10A illustrates the seventh representative gasket located by akeeper and positioned within fluid conduit port counterbores prior tothe application of axial sealing force to make the joint; and

FIG. 10B illustrates the seventh representative gasket in fluid conduitport counterbores after the joint has been made.

DETAILED DESCRIPTION

The examples of the apparatus and methods discussed herein are notlimited in application to the details of construction and thearrangement of components set forth in the following description orillustrated in the drawings. The apparatus and methods are capable ofother embodiments and of being practiced or of being carried out invarious ways. Also, the phrasing and terminology used herein is for thepurpose of description and should not be regarded as limiting. The useof “including,” “comprising,” or “having,” “containing,” “involving,”and variations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

Making fluid pathway joints with sealing integrity sufficient tominimize leakage on a molecular level (e.g., helium leak rate less than1×10e-9.std.cc/sec) involves special design considerations. Amongskilled designers it is known that making a joint successfully matingmetallic fluid delivery apparatus elements using a metallic gasketbenefits greatly from plastic deformation of the gasket sealing regionthat is in contact with the apparatus elements. Suitable deformationbecomes more difficult to achieve when changing from gasket materialswith relatively large Poisson's Ratio and lower yield strength, such ascopper, to gasket materials with smaller Poisson's Ratio and higheryield strength like stainless steels. Additionally, substantial axialforce may be necessary to achieve any axial strain in a metallic gasket.One design approach involves making a gasket with axially orientedsealing regions having substantially reduced contact area to encourageplastic deformation of the sealing regions of the gasket without aproblematic large increase of the required axial joining force.

A related and often simultaneously used technique to more easily achievegasket plastic deformation is to anneal the gasket material into amaximally soft condition. Another known design challenge is therelatively high Young's Modulus (Modulus of Elasticity) of metalscausing relatively small reversible metallic gasket rebound afterelastic deformation and also limiting the amount of strain that may beimparted to a metallic gasket before plastic deformation occurs. As isknown in the study of the mechanics of materials, annealing does notappreciably affect the stiffness (Modulus of Elasticity) of the gasketbut will appreciably lower its yield strength. The strain-hardeningwhich occurs subsequent to initial yield of many gasket materials can bea significant contributor to the eventual rebound properties of thegasket. A further design challenge is the fact a gasket lackingsufficient bulk hardness may exhibit cold flow relaxation over time andthereby develop a leak despite having been suitably tight initially.

The preceding problematic deformation characteristics may make jointaxial dimension tolerances more critical than is desirable in massproduction situations and also pose problems which may be described asresidual expansion force within a gasket being insufficient to ensureseal integrity. A design solution to these challenges selectivelyexcludes material from the bulk of a ring-shaped part to create a gasketcross-sectional profile inducing intentional and effective stressconcentration. This stress concentration causes less axial force to beneeded when producing net elastic axial strain and likely producesstrain-hardening in some interior regions of the gasket bulk. Theresulting reversible elastic axial displacement versus axial forcerelationship provides a gasket which exhibits greater rebound thanotherwise available, and consequently makes a more reliable joint withless total required apparatus element mating force. The exclusion ofmaterial may be accomplished, for example, by machining away portions asin the Doyle patents and Spence & Felber patent cited previously, or byforming sheet stock into a torus of “C”-shaped cross-section as shown inU.S. Pat. Nos. 5,730,448 and 5,713,582 both issued to Swensen et al., orthe desired spring-like behavior can be obtained by actuallyincorporating a toroidal spring as in the Inagaki patent, among othermanufacturing techniques. The designs of Doyle and Spence & Felberremove material in a radial direction and are therefore limited byrequirements for guaranteed minimum wall thickness between the gasketinternal fluid pathway and the exterior environment. Manufacturingtolerances may have adverse consequences in this regard as well.

In many of the previously cited U.S. Patent examples there isconsiderable risk of adversely scratching the axially oriented sealingregion of a gasket prior to joint assembly and such damage therebymaking a joint free of leaks unachievable. Gasket centering by aseparate retainer provides desirable consistency of alignment betweenthe fluid pathway conduit ports and the central passageway through thegasket. Within some fluid delivery apparatus or devices used forsemiconductor manufacturing processes there are situations usingmultiple types of fluid pathway joints simultaneously and therefore agasket structure allowing independent tailoring of the physical shape ofthe gasket sealing surfaces on opposing gasket sealing regions and/orthe mechanical behavior of opposing gasket sealing regions is desired.

A first representative example 100 of Applicant's ring-shaped gasket isillustrated in FIG. 1A and FIG. 1B. The gasket body 150 is piercedthrough by a hole 151 defining a fluid pathway bore 155 comprising aninner radial surface 156 which may conveniently be substantiallystraight to reduce fluid turbulence in the fluid delivery apparatuscoupling joint. The outer radial extent of the gasket body is defined bya radial outer surface 190 which may have a circumferential groove 192to accommodate a keeper (not shown in FIG. 1A) for locating the gasket100 in a fluid delivery component assembly (also not shown in FIG. 1A).

The first representative gasket example may have a first axial endsurface 110 including a stress concentration feature 120 which appearsas a groove in the first axial end surface 110. The stress concentrationgroove 120 removes gasket body material from the region immediatelyadjacent the intended gasket sealing region to thereby form a lip 130which desirably projects axially outward beyond the first axial endsurface prior to making the joint. The lip 130 includes an axiallyprominent protective ridge 132 and an immediately adjacent sealingsurface 134. In the event the gasket is slid across a rough surface,during normal factory handling, the protective ridge 132 may be damagedbut the sealing surface 134 will remain pristine. The sealing surface134 is a circumferential sector exhibiting a generally constant anglewith respect to the gasket bore 155 axis, and also to the plane of thefirst axial end surface 110, but may advantageously have a slightlyconvex shape for some gasket materials. The gasket sealing region lip130 may be appreciated as resembling a frustoconical shell flaringoutward from the gasket bore 155 toward the radial outer surface 190.The radial extent of the sealing surface 134 is beneficially greaterthan the reduced contact area of prior designs so as to create aradially much longer leak resisting contact between the gasket and fluidconduit port face. When the gasket 100 is made into a leak tight fluidpathway joint by axial compression between opposing flat apparatusfaces, the protective ridge 132 will be plastically deformed and thesealing surface 134 slightly deflected radially outward contacting theflat apparatus face, in concert with further axial compression, byvirtue of the groove 120 allowing the lip 130 to bend over.

The first representative gasket example may have a second axial endsurface 160 including a stress concentration feature 170 which appearsas a groove in the second axial end surface 160. The stressconcentration groove 170 removes gasket body material from the regionimmediately adjacent the intended gasket sealing region to thereby forma lip 180 which desirably projects axially outward beyond the secondaxial end surface prior to making the joint. The lip 180 includes anaxially prominent protective ridge 182 and an immediately adjacentsealing surface 184. In the event the gasket is slid across a roughsurface, during normal factory handling, the protective ridge 182 may bedamaged but the sealing surface 184 will remain pristine. The sealingsurface 184 is a circumferential sector exhibiting a generally constantangle with respect to the gasket bore 155 axis, and also to the plane ofthe second axial end surface 160, but may advantageously have a slightlyconvex shape for some gasket materials. The radial extent of the sealingsurface 184 is beneficially greater than the reduced contact area ofprior designs so as to create a radially much longer leak resistingcontact between the gasket and fluid conduit port face. When the gasket100 is made into a leak tight fluid pathway joint by axial compressionbetween opposing flat apparatus faces, the protective ridge 182 will beplastically deformed and the sealing surface 184 slightly deflectedradially outward contacting the flat apparatus face, in concert withfurther axial compression, by virtue of the groove 170 allowing the lip180 to bend over.

Gasket designers can appreciate how the axial end surfaces 110,160 mayfunction as relatively hard stops preventing excessive compression ofthe gasket lips 130,180 by contacting the face surface of thecorresponding fluid conduit ports. Very minor compositional andmanufacturing variations within the gasket 100 may cause an axial endsurface 110,160 to contact the corresponding fluid conduit port facebefore the other axial end surface 160,110 during the process of gasketcompression as the joint is being made. The noted hard stop functionensures both opposed gasket lips 130,180 are eventually compressedequally and fully. It should also be appreciated that the end regions157,158 of the fluid pathway bore 155 will preferably have less axialextent than the axial end surfaces 110,160 to prevent formation ofvirtual leak cavities within the fluid pathway when the joint is fullymated. Designers may also understand the existence of unaltered centralmaterial within the gasket body 150 makes deformation behavior of thefirst axial end surface lip 130 substantially independent of thedeformation behavior of the second axial end surface lip 180.

A second representative example 200 of Applicant's ring-shaped gasket isillustrated in FIG. 2A and FIG. 2B and is similar to the first example.The gasket body 250 is pierced through by a hole 251 defining a fluidpathway bore 255 comprising an inner radial surface 256 which mayconveniently be substantially straight to reduce fluid turbulence in thefluid delivery apparatus coupling joint. The outer radial extent of thegasket body is defined by a radial outer surface 290 which may have acircumferential groove 292 to accommodate a keeper (not shown in FIG. 2Anor FIG. 2B) for locating the gasket 200 in a fluid delivery componentassembly (also not shown).

The second representative gasket example may have first 210 and second260 axial end surfaces including stress concentration features 220,270which appear as grooves in the axial end surfaces 210,260. The stressconcentration grooves 220,270 remove gasket body material from theregion immediately adjacent both intended gasket sealing regions tothereby form lips 230,280 on the axial end surfaces 210,260 which lipsdesirably project axially outward beyond the corresponding axial endsurfaces 210,260 prior to making the joint. The stress concentrationgrooves 220,270 have inner walls 221,271 closest the gasket radial innersurface 256 forming an acute angle with the plane of each associatedgasket axial end surface 210,260 thereby forming an undercut of eachgasket sealing region. The lips 230,280 each include an axiallyprominent protective ridge 232,282 and an immediately adjacent sealingsurface 234,284. In the event the gasket is slid across a rough surface,during normal factory handling, the protective ridges 232,282 may bedamaged but the sealing surfaces 234,284 will remain pristine. Thesealing surfaces 234,284 are circumferential sectors exhibiting agenerally constant angle with respect to the gasket bore 255 axis, andalso to the plane of each associated axial end surface 210,260, but mayadvantageously have a slightly convex shape for some gasket materials.The gasket sealing region lips 230,280 may be appreciated as resemblingopposite directed frustoconical shells flaring outward from the gasketbore 255 toward the radial outer surface 290. The radial extent of thesealing surfaces 234,284 is beneficially greater than the reducedcontact area of prior designs so as to create a radially much longerleak resisting contact between the gasket and fluid conduit port face.When the gasket 200 is made into a leak tight fluid pathway joint byaxial compression between opposing flat apparatus faces, the protectiveridges 232,282 will be plastically deformed and the sealing surfaces234,284 slightly deflected radially outward contacting the flatapparatus faces in concert with further axial compression, as aconsequence of the undercut grooves 220,270 allowing the gasket lips230,280 to controllably bend.

In similar consideration of the second representative gasket example,designers can appreciate how the axial end surfaces 210,260 may functionas relatively hard stops preventing excessive compression of the gasketlips 230,280 by contacting the face surface of the corresponding fluidconduit ports. Very minor compositional and manufacturing variationswithin the gasket 200 may cause an axial end surface 210,260 to contactthe corresponding fluid conduit port face before the other axial endsurface 260,210 during the process of gasket compression as the joint isbeing made. The noted hard stop function ensures both opposed gasketlips 230,280 are eventually compressed equally and fully. It should alsobe appreciated that the end regions 257,258 of the fluid pathway bore255 will preferably have less axial extent than the axial end surfaces210,260 to prevent formation of virtual leak cavities within the fluidpathway when the joint is fully mated. Designers may also understand theexistence of unaltered central material within the gasket body 250 makesdeformation behavior of the first axial end surface lip 230substantially independent of the deformation behavior of the secondaxial end surface lip 280. This independence of deformation behaviorbetween the opposite axial end surface lips 230,280 can allow, at thedesigner's choice, fabrication of gaskets having intentionally differentcharacteristics on opposite sides. Skilled designers will appreciatethat lip bending characteristics may be adjusted by choice of theundercut acute angle along with groove depth and width. Thus, forexample, one or more of the undercut acute angle, the groove depth, andthe groove width may be different on one side of the gasket relative tothe undercut acute angle, the groove depth, or the groove width on theopposing side of the gasket. Further, a ring-shaped gasket may beprovided with a stress concentration groove on one axial end surfacethat is similar to stress concentration groove 120 illustrated in FIGS.1A-1C, and a stress concentration groove on the opposing axial endsurface that is similar to stress concentration groove 220 illustratedin FIGS. 2A-2C in which an inner wall 271 of the stress concentrationgroove 220 closest to the gasket inner radial surface is formed at anacute angle with the plane of gasket axial end surface 260. Accordingly,the use of first and second axial end surface designs which arecompletely different from each other in physical structure and/ordeformation behavior is also contemplated as described further below.

Designers experienced in high purity applications will appreciate thedesirability of placing stress concentration features 220,270 outsidethe “wetted” fluid pathway, to minimize pathway pockets which mightcapture contaminants, with the resultant design having the gasketsealing region lips 230,280 flaring outward from the gasket bore 255.Applications more concerned with sealing relatively high pathwayinternal pressures will likely benefit from a fluid energized sealingeffect obtainable by having the gasket sealing region lips flaringinward toward the gasket bore. In such an alternative design theinternal fluid pressure will then push against the inward flared gasketsealing lips and urge them against their corresponding apparatuselements to effect a tighter seal along the radial contact area. Thissort of alternative gasket embodiment would necessarily have one or morestress concentration features being placed closest to the gasket boreand the adjacent sealing region lips being radially farther from thegasket bore.

A third representative example 300 of Applicant's ring-shaped gasket isillustrated in FIG. 3A, FIG. 3B, and FIG. 3C. The gasket body 350 ispierced through by a hole 351 defining a fluid pathway bore 355comprising an inner radial surface 356 which may conveniently besubstantially straight to reduce fluid turbulence in the fluid deliveryapparatus coupling joint. The outer radial extent of the gasket body isdefined by a radial outer surface 390 which may have a circumferentialgroove 392 to accommodate a keeper (not shown in FIG. 3A, 3B, nor 3C)for locating the gasket 300 in a fluid delivery component assembly (alsonot shown in the Figures).

The third representative gasket example may have a first axial endsurface 310 including a stress concentration feature 320 comprised of aregular arrangement of blind cavities projecting into the first axialend surface 310. The stress concentration cavities 325,326,327, et seq.,remove gasket body material from the region immediately adjacent theintended gasket sealing region to thereby form a lip 330 on the axialfirst end surface 310 which desirably projects axially outward beyondthe first axial end surface prior to making the joint. The lip 330includes an axially prominent protective ridge 332 and an immediatelyadjacent sealing surface 334. The sealing surface 334 is acircumferential sector exhibiting a generally constant angle withrespect to the gasket bore 355 axis, and also to the plane of the firstaxial end surface 310, but may advantageously have a slightly convexshape for some gasket materials. The gasket sealing region lip 330 maybe appreciated as resembling a frustoconical shell flaring outward fromthe gasket bore 355 toward the radial outer surface 390. The radialextent of the sealing surface 334 is beneficially greater than thereduced contact area of prior designs so as to create a radially muchlonger leak resisting contact between the gasket and fluid conduit portface. In the event the gasket is slid across a rough surface, duringnormal factory handling, the protective ridge 332 may be damaged but thesealing surface 334 will remain pristine. When the gasket 300 is madeinto a leak tight fluid pathway joint by axial compression betweenopposing flat apparatus faces, the protective ridge 332 will beplastically deformed and the sealing surface 334 slightly deflectedradially outward, in concert with further axial compression, by virtueof the cavities 325,326,327, et seq., allowing the lip 330 to bend over.

The third representative gasket example may have a second axial endsurface 360 including a stress concentration feature 370 that includes aregular arrangement of blind cavities projecting into the second axialend surface 360. The stress concentration cavities 375,376,377, et seq.,remove gasket body material from the region immediately adjacent theintended gasket sealing region to thereby form a lip 380 on the secondaxial end surface 360 which desirably projects axially outward beyondthe corresponding axial end surface prior to making the joint. The lip380 includes an axially prominent protective ridge 382 and animmediately adjacent sealing surface 384. The sealing surface 384 is acircumferential sector exhibiting a generally constant angle withrespect to the gasket bore 355 axis, and also to the plane of the secondaxial end surface 360, but may advantageously have a slightly convexshape for some gasket materials. The radial extent of the sealingsurface 384 is beneficially greater than the reduced contact area ofprior designs so as to create a radially much longer leak resistingcontact between the gasket and fluid conduit port face. In the event thegasket is slid across a rough surface, during normal factory handling,the protective ridge 382 may be damaged but the sealing surface 384 willremain pristine. When the gasket 300 is made into a leak tight fluidpathway joint by axial compression between opposing flat apparatusfaces, the protective ridge 382 will be plastically deformed and thesealing surface 384 slightly deflected radially outward, in concert withfurther axial compression, by virtue of the cavities 375,376,377, etseq. allowing the lip 380 to bend over. Although the stressconcentration cavities 325,326,327 and 375,376,377 disposed on opposingaxial faces of the gasket 300 are illustrated to be in phase with oneanother around the circumference of the gasket, it should be appreciatedthat they may instead be disposed in anti-phase with one another, asdescribed further below with respect to FIG. 5A and FIG. 5B.

In similar consideration of the third representative gasket example,designers can appreciate how the axial end surfaces 310,360 may functionas relatively hard stops preventing excessive compression of the gasketlips 330,380 by contacting the face surface of the corresponding fluidconduit ports. Very minor compositional and manufacturing variationswithin the gasket 300 may cause an axial end surface 310,360 to contactthe corresponding fluid conduit port face before the other axial endsurface 360,310 during the process of gasket compression as the joint isbeing made. The noted hard stop function ensures both opposed gasketlips 330,380 are eventually compressed equally and fully. It should alsobe appreciated that the end regions 357,358 of the fluid pathway bore355 will preferably have less axial extent than the axial end surfaces310,360 to prevent formation of virtual leak cavities within the fluidpathway when the joint is fully mated. Designers may also understand theexistence of unaltered central material within the gasket body 350 makesdeformation behavior of the first axial end surface lip 330substantially independent of the deformation behavior of the secondaxial end surface lip 380.

A fourth representative example 400 of Applicant's ring-shaped gasketillustrated in FIG. 4A and FIG. 4B is similar to the third example. Thegasket body 450 is pierced through by a hole 451 defining a fluidpathway bore 455 comprising an inner radial surface 456 which mayconveniently be substantially straight to reduce fluid turbulence in thefluid delivery apparatus coupling joint. The outer radial extent of thegasket body is defined by a radial outer surface 490 which may have acircumferential groove 492 to accommodate a keeper (not shown in FIG. 4Anor FIG. 4B) for locating the gasket 400 in a fluid delivery componentassembly (also not shown).

The fourth representative gasket example may have first 410 and second460 axial end surfaces including stress concentration features 420,470including regular arrangements of blind cavities 425,475 projecting intoboth the axial end surfaces 410,460. The stress concentration cavities425,475 remove gasket body material from the region immediately adjacentboth intended gasket sealing regions to thereby form lips 430,480 on theaxial end surfaces 410,460 which lips desirable project axially outwardbeyond the corresponding axial end surfaces 410,460 prior to making thejoint. Each cavity among the plurality of stress concentration cavities425,475 has individual volumetric axes 421,471 forming an acute anglewith the plane of the associated gasket axial end surface 410,460thereby forming a plurality of undercuts of the gasket sealing regions.The lips 430,480 each include an axially prominent protective ridge432,482 and an immediately adjacent sealing surface 434,484. In theevent the gasket is slid across a rough surface, during normal factoryhandling, the protective ridges 432,482 may be damaged but the sealingsurfaces 434,484 will remain pristine. The sealing surfaces 434,484 arecircumferential sectors exhibiting a generally constant angle withrespect to the gasket bore 455 axis, and also to the plane of eachassociated axial end surface 410,460, but may advantageously have aslightly convex shape for some gasket materials. The gasket sealingregion lips 430,480 may be appreciated as resembling opposite directedfrustoconical shells flaring outward from the gasket bore 455 toward theradial outer surface 490. The radial extent of the sealing surfaces434,484 is beneficially greater than the reduced contact area of priordesigns so as to create a radially much longer leak resisting contactbetween the gasket and fluid conduit port face. When the gasket 400 ismade into a leak tight fluid pathway joint by axial compression betweenopposing flat apparatus faces, the protective ridges 432,482 will beplastically deformed and the sealing surfaces 434,484 slightly deflectedradially outward in concert with further axial compression, as aconsequence of the undercut cavities 425,475 allowing the gasket lips430,480 to controllably bend.

In similar consideration of the fourth representative gasket example,designers can appreciate how the axial end surfaces 410,460 may functionas relatively hard stops preventing excessive compression of the gasketlips 430,480 by contacting the face surface of the corresponding fluidconduit ports. Very minor compositional and manufacturing variationswithin the gasket 400 may cause an axial end surface 410,460 to contactthe corresponding fluid conduit port face before the other axial endsurface 460,410 during the process of gasket compression as the joint isbeing made. The noted hard stop function ensures both opposed gasketlips 430,480 are eventually compressed equally and fully. It should alsobe appreciated that the end regions 457,458 of the fluid pathway bore455 will preferably have less axial extent than the axial end surfaces410,460 to prevent formation of virtual leak cavities within the fluidpathway when the joint is fully mated. Designers may also understand theexistence of unaltered central material within the gasket body 450 makesdeformation behavior of the first axial end surface lip 430substantially independent of the deformation behavior of the secondaxial end surface lip 480.

Skilled gasket designers will further appreciate the first and secondaxial end surface shapes acting relatively independently alsocontemplates a design combination comprised of a stress concentrationgroove on one face and a plurality of stress concentration cavities onthe opposite face. For example, in some embodiments, the stressconcentration feature on one face may be similar to the stressconcentration grooves 120,170 of FIGS. 1A-C, or the stress concentrationgrooves 220,270 of FIGS. 2A-C, while the stress concentration feature onthe opposing face may include a plurality of stress concentrationcavities similar to the stress concentration cavities 325,326,327 ofFIGS. 3A-C, or the stress concentration cavities 425,475 of FIGS. 4A-B.Additionally, when a plurality of stress concentration cavities isdesigned into both the first and second axial end surfaces, then theindividual volumetric axes of opposing cavities may be circumferentiallyaligned as in FIG. 4A or may alternatively be interleaved as in FIG. 5Aand FIG. 5B illustrating a fifth gasket example 500. Correspondingelements in FIG. 5A include a gasket body 550, an inner radial surface556, a first axial end surface 510 with lip 530 and associated blindcavities 525, and a second axial end surface 560 with lip 580 andassociated blind cavities 565. The top plan view in FIG. 5B shows howthe cross sectioned illustration reveals the cavities of one axial endsurface are substantially anti-phase interposed with the cavities of theopposite axial end surface. It should also be appreciated FIG. 5Aillustrates a gasket wherein the radial outer surface 590 lacks a groovefor a keeper since the keeper groove is optional in all examples.

FIG. 6A and FIG. 6B illustrate how a seal is effected when a ring-shapedmetallic gasket of the fourth exemplary shape 400 is compressed betweenopposing apparatus elements 605,660 having simple flat surfaces 630,680in contact with the gasket 400. The sealing region lips 430,480initially contact the fluid delivery apparatus element flat surfaces630,680 along the protective ridges 432,482 when the apparatus elements605,660 are urged toward each other by fasteners or mating componentthreads as illustrated in FIG. 6A. A thin keeper 495 engaged with anexterior circumferential groove 492 may assist with positioning of thegasket 400 between the opposing fluid conduit ports 610,690. Asillustrated in FIG. 6B after complete axial compression of the made-upjoint, the opposing apparatus elements 605,660 abut the gasket axial endsurfaces 410,460 and the gasket lips 430,480 have bent outward so thatthe sealing surfaces 434,484 have come into flat contact with thecorresponding fluid delivery apparatus element fluid conduit port facesurfaces 614,664. It should be appreciated that the radial extent of theradial outer surface 490 of the gasket 400 is preferably less than theradial extent of the flat surfaces 630,680 of the opposing apparatuselements, both before and after compression between the opposingapparatus elements 605,660, as shown in FIGS. 6A and 6B.

A sixth representative example 700 of Applicant's ring-shaped gasket isillustrated in FIG. 7A and FIG. 7B. The gasket body 750 is piercedthrough by a hole defining a fluid pathway bore 755 comprising an innerradial surface 756 which may conveniently be substantially straight toreduce fluid turbulence in the fluid delivery apparatus coupling joint.The outer radial extent of the gasket body is defined by a radial outersurface 790 which may have a circumferential groove 792 to accommodate akeeper (not shown in FIG. 7A nor FIG. 7B) for locating the gasket 700 ina fluid delivery component assembly (also not shown).

The sixth representative gasket example may have a first axial endsurface 710 including a stress concentration feature that includes aregular arrangement of blind cavities 718,719,720, et seq. & 725,726,727et seq. projecting into the first axial end surface 710. The stressconcentration cavities 725, etc. remove gasket body material from theregion immediately adjacent the intended gasket sealing region tothereby form a lip 730 on the first axial end surface 710 which lipdesirably projects axially outward beyond the corresponding first axialend surface 710 prior to making the joint. Each cavity among theplurality of stress concentration cavities 725, etc. has individualvolumetric axes 721 forming an acute angle with the plane of theassociated first gasket axial end surface 710 thereby forming aplurality of undercuts of the gasket sealing region. The lip 730includes an axially prominent protective ridge 732 and an immediatelyadjacent sealing surface 734. In the event the gasket is slid across arough surface, during normal factory handling, the protective ridge 732may be damaged but the sealing surface 734 will remain pristine. Thesealing surface 734 is a circumferential sector exhibiting a generallyconstant angle with respect to the gasket bore 755 axis, and also to theplane of the associated first axial end surface 710, but mayadvantageously have a slightly convex shape for some gasket materials.The radial extent of the sealing surface 734 is beneficially greaterthan the reduced contact area of prior designs so as to create aradially much longer leak resisting contact between the gasket and fluidconduit port face. When the gasket 700 is made into a leak tight fluidpathway joint by axial compression between opposing flat apparatusfaces, the protective ridge 732 will be plastically deformed and thesealing surface 734 slightly deflected radially outward in concert withfurther axial compression, as a consequence of the undercut cavities725, etc. allowing the gasket lip 730 to controllably bend. It should beappreciated a groove stress concentration feature, as previouslydescribed in the first and second gasket examples, may alternatively beused on the first axial end surface of the presently described gasketexample. Such an alternative example 701 of Applicant's sixthrepresentative gasket example is illustrated in FIG. 7C, in whichreference designators 710,720,730,732,734, and 757 correspond tofeatures 110,120,130,132,134, and 157 described previously with respectto FIGS. 1A-C. Although not shown, it should be appreciated that astress concentration groove similar to that described with respect toFIGS. 2A-C could alternatively be used.

The sixth representative gasket example may have a second axial endsurface 760 including an exterior chamfer 770 blending into the radialouter surface 790 for convenience. A sealing region 785 initially flatin a radial direction, suitable for use with fluid delivery elementshaving annular projections surrounding circular conduit openings, isformed as a circumferential sector generally perpendicular with respectto the gasket bore 755 axis and parallel to the plane of the secondaxial end surface 760. The axial extent of the initially flat sealingregion 785 may advantageously be less than the second axial end surface760 so as to be effectively recessed within the second axial end surface760. In the event the gasket is slid across a rough surface, duringnormal factory handling, the second axial end surface 760 may be damagedbut the sealing surface 785 will remain pristine. When the gasket 700 ismade into a leak tight fluid pathway joint by axial compression betweenopposing fluid delivery element conduit ports, an annular projectionwill cause permanent plastic deformation of the gasket sealing region785 as further described below.

In consideration of the sixth representative gasket example, designerscan appreciate how the first axial end surface 710 may function as arelatively hard stop preventing excessive compression of the gasket lip730 by contacting the face surface of a corresponding first fluidconduit port. It should also be appreciated that the first end region757 of the fluid pathway bore 755 will preferably have less axial extentthan the first axial end surface 710 to prevent formation of virtualleak cavities within the fluid pathway when the joint is fully mated.Designers may also understand the existence of unaltered centralmaterial within the gasket body 750 makes deformation behavior of thefirst axial end surface lip 730 substantially independent of thedeformation behavior of the second axial end surface sealing region 785.This independence of deformation behavior is used to advantage in thesixth representative gasket example as further described below withrespect to FIG. 8A and FIG. 8B.

FIG. 8A and FIG. 8B illustrate how a seal is effected when a ring-shapedmetallic gasket of the sixth exemplary shape 700 is compressed betweenopposing fluid delivery apparatus elements 805,860. FIG. 8A illustratesthe sixth representative gasket located by a keeper 795 and positionedbetween an upper fluid conduit port counterbore 830 having a flat bottomand a lower fluid conduit port counterbore 880 having a shaped annularprojection 885 prior to application of axial sealing force to make thejoint. FIG. 8B illustrates the sixth representative gasket 700 betweencorresponding fluid conduit port counterbores after the joint has beenmade. The sealing region lip 730 initially contacts the fluid deliveryapparatus element flat surface 830 along the protective ridge 732, andthe initially flat sealing region 785 contacts the annular projection885, when the apparatus elements 805,860 are urged toward each other byfasteners (or mating component threads or other means) as illustrated inFIG. 8A. The thin keeper 795 engaged with an exterior circumferentialgroove 792 may assist with positioning of the gasket 700 between theopposing fluid conduit ports 810,890. During the process of gasketcompression, as the joint is being made, the hard stop function of thefirst axial end surface 710 contacting against the upper fluid conduitport counterbore 830 ensures all additional closing motion, joining theopposed fluid conduit ports 810,890, will result in proper indentationof the initially flat sealing region 785 by the lower fluid conduit portannular projection 885. As illustrated in FIG. 8B after complete axialcompression of the made-up joint, the gasket lip 730 has bent outward sothat the sealing surface 734 comes into flat contact with thecorresponding fluid delivery apparatus element fluid conduit port facesurface 830 while the initially flat sealing region 785 has beendeformed by the annular projection 885 pressing into same. When theapparatus elements 805,860 contact the keeper 795 no further gasketcompression is feasible. The axial extent of the second axial endsurface 760 may be chosen in conjunction with thickness of the keeper795 so as to ensure a gap between the second axial end surface 760 andthe bottom of the lower fluid conduit port counterbore 880. A gap may bedesired to ensure sealing occurs only between the shaped annularprojection 885 and the initially flat (but now deformed) second axialend surface sealing region 785 while also allowing helium leak detectionmethods of testing joint integrity. It should be appreciated that theradial extent of the radial outer surface 790 of the gasket 700 ispreferably less than the radial extent of the counterbore 830 of thefluid delivery apparatus element 805 and the radial extent of thecounterbore 880 of the fluid delivery apparatus element 860, both beforeand after compression between the opposing apparatus elements 805,860,as shown in FIGS. 8A and 8B.

A seventh representative example 900 of Applicant's ring-shaped gasketis illustrated in FIG. 9A and FIG. 9B and is similar to the first andsecond representative examples. The gasket body 950 is pierced throughby a hole 951 defining a fluid pathway bore 955 comprising an innerradial surface 956 which may conveniently be substantially straight toreduce fluid turbulence in the fluid delivery apparatus coupling joint.The outer radial extent of the gasket body is defined by a radial outersurface 990 which may again have a circumferential groove 992 toaccommodate a keeper (not shown in FIG. 9A nor FIG. 9B) for locating thegasket 900 in a fluid delivery component assembly (also not shown). Thepresence of groove 992 to accommodate a keeper is optional in thisrepresentative example, as previously described with respect to theprior representative gasket examples.

The seventh representative gasket example may have first 910 and second960 axial end surfaces including stress concentration features 920,970which again appear as grooves in the axial end surfaces 910,960. Thestress concentration grooves 920,970 remove gasket body material fromthe region immediately adjacent both intended gasket sealing regions tothereby form lips 930,980 on the axial end surfaces 910,960 which lipsdesirably project axially outward beyond the corresponding axial endsurfaces 910,960 prior to making the joint. In a manner similar to thatof the second representative gasket example illustrated in FIGS. 2A and2B, the stress concentration grooves 920,970 have inner walls closestthe gasket radial inner surface 956 that form an acute angle with theplane of each associated gasket axial end surface 910,960 therebyforming an undercut of each gasket sealing region. However, in contrastto the second representative gasket example of FIGS. 2A and 2B, thestress concentration grooves 920,970 of this seventh representativegasket example have radially inner and outer groove walls that aresubstantially parallel to one another thereby defining a U-shapedgroove, rather than the substantially V-shaped grooves 220,270 depictedin the second representative gasket example of FIGS. 2A and 2B. Thesubstantially parallel radially inner and outer groove walls of thestress concentration grooves 920,970 thereby each form an acute anglewith the plane of each associated gasket axial end surface 910,960. Asin the previously described representative gasket examples, the lips930,980 each include an axially prominent protective ridge 932,982 andan immediately adjacent sealing surface 934,984. In the event the gasketis slid across a rough surface, for example, during normal factoryhandling, the protective ridges 932,982 may be damaged but the sealingsurfaces 934,984 will remain pristine. The sealing surfaces 934,984 arecircumferential sectors exhibiting a generally constant angle withrespect to the gasket bore 955 axis, and also to the plane of eachassociated axial end surface 910,960, but as previously described mayadvantageously have a slightly convex shape for some gasket materials.It will be appreciated that the gasket sealing region lips 930,980 mayagain resemble opposite directed frustoconical shells flaring outwardfrom the gasket bore 955 toward the radial outer surface 990. As in thepreviously described representative gasket examples, the radial extentof the sealing surfaces 934,984 is beneficially greater than the reducedcontact area of prior designs so as to create a radially much longerleak resisting contact between the gasket and fluid conduit port face.When the gasket 900 is made into a leak tight fluid pathway joint byaxial compression between opposing flat apparatus faces, the protectiveridges 932,982 will be plastically deformed and the sealing surfaces934,984 slightly deflected radially outward contacting the flatapparatus faces in concert with further axial compression, as aconsequence of the undercut grooves 920,970 allowing the gasket lips930,980 to controllably bend, as described further with respect to FIGS.10A and 10B.

In similar consideration of the previously described representativegasket examples, designers can appreciate how the axial end surfaces910,960 may function as relatively hard stops preventing excessivecompression of the gasket lips 930,980 by contacting the face surface ofthe corresponding fluid conduit ports. Very minor compositional andmanufacturing variations within the gasket 900 may cause an axial endsurface 910,960 to contact the corresponding fluid conduit port facebefore the other axial end surface 960,910 during the process of gasketcompression as the joint is being made. However, the noted hard stopfunction ensures both opposed gasket lips 930,980 are eventuallycompressed equally and fully. It should also be appreciated that the endregions 957,958 of the fluid pathway bore 955 will preferably have lessaxial extent than the axial end surfaces 910,960 to prevent formation ofvirtual leak cavities within the fluid pathway when the joint is fullymated.

Skilled designers will appreciate the existence of unaltered centralmaterial within the gasket body 950 makes deformation behavior of thefirst axial end surface lip 930 substantially independent of thedeformation behavior of the second axial end surface lip 980. Thisindependence of deformation behavior between the opposite axial endsurface lips 930,980 can allow, at the designer's choice, fabrication ofgaskets having intentionally different characteristics on oppositesides. Skilled designers will appreciate that lip bendingcharacteristics may be adjusted by choice of the undercut acute anglealong with groove depth and width. Thus, for example, one or more of theundercut acute angle, the groove depth, and the groove width may bedifferent on one side of the gasket relative to the undercut acuteangle, the groove depth, or the groove width on the opposing side of thegasket. Further, a ring-shaped gasket may be provided with a stressconcentration groove on one axial end surface that is similar to thestress concentration groove 120 illustrated in FIGS. 1A-1C, or thestress concentration groove 220 illustrated in FIGS. 2A-2C, with theother stress concentration feature on the opposing axial end surfacebeing similar to the stress concentrations grooves 920 or 970 describedabove. Alternatively still, ring-shaped gaskets may be provided with astress concentration feature on one axial end surface that is similar tothe stress concentration grooves 920,970 described above, with theopposing axial end surface being constructed to form a fluid tight sealwith fluid delivery elements having annular projections surroundingcircular conduit openings in the manner previously described withrespect to FIGS. 7A and 7B. Accordingly, it should be appreciated thatthe various representative gasket designs disclosed herein are notlimited to gaskets having substantially symmetric axial end surfaces, asthe use of first and second axial end surface designs which arecompletely different from each other in physical structure and/ordeformation behavior is also contemplated.

Designers experienced in high purity applications will appreciate thedesirability of placing stress concentration features 920,970 outsidethe “wetted” fluid pathway, to minimize pathway pockets which mightcapture contaminants, with the resultant design having the gasketsealing region lips 930,980 flaring outward from the gasket bore 955.Applications more concerned with sealing relatively high pathwayinternal pressures will likely benefit from a fluid energized sealingeffect obtainable by having the gasket sealing region lips flaringinward toward the gasket bore. In such an alternative design theinternal fluid pressure will then push against the inward flared gasketsealing lips and urge them against their corresponding apparatuselements to effect a tighter seal along the radial contact area. Thissort of alternative gasket embodiment would necessarily have one or morestress concentration features being placed closest to the gasket boreand the adjacent sealing region lips being radially farther from thegasket bore.

FIG. 10A and FIG. 10B illustrate how a seal is effected when aring-shaped metallic gasket of the seventh exemplary shape 900 iscompressed between opposing apparatus elements 605,660 having simpleflat surfaces 630,680 in contact with the gasket 900. The sealing regionlips 930,980 initially contact the fluid delivery apparatus element flatsurfaces 630,680 along the protective ridges 932,982 when the apparatuselements 605,660 are urged toward each other by fasteners or matingcomponent threads as illustrated in FIG. 10A. A thin keeper 995 engagedwith an exterior circumferential groove 992 of the gasket 900 may assistwith positioning of the gasket 900 between the opposing fluid conduitports 610,690. As illustrated in FIG. 10B after complete axialcompression of the made-up joint, the opposing apparatus elements605,660 abut the gasket axial end surfaces 910,960 and the gasket lips930,980 have bent outward so that the sealing surfaces 934,984 have comeinto flat contact with the corresponding fluid delivery apparatuselement fluid conduit port face surfaces 614,664. It should beappreciated that the radial extent of the radial outer surface 990 ofthe gasket 900 is again preferably less than the radial extent of theflat surfaces 630,680 of the opposing apparatus elements, both beforeand after compression between the opposing apparatus elements 605,660 asshown in FIGS. 10A and 10B.

The various gasket designs described herein are particularly useful inhigh purity fluid delivery apparatus situations wherein gasket materialsmay have mechanical properties similar to the apparatus elementsintended to be sealingly joined in fluid communication. The use of fluiddelivery system components made from high purity 316L stainless steelwith fluid conduit ports having flat-bottomed counterbores is wellknown. The difficulties of achieving molecular level leak tightness withsuch components can be lessened by using the described designs. In highpurity liquid delivery apparatus made from polymer materials there areessentially identical problems and these designs are similarlyapplicable to those situations too.

As should be appreciated in view of the above disclosure, the variousgasket designs described herein permit opposing axial faces of thegasket to be independently tailored to meet the physical and mechanicalrequirements of the adjacent face surface of the fluid deliveryapparatus against which they abut. Thus, for example, the gasket sealingsurface on one side of the gasket may be constructed to sealingly engagean annular projection surrounding a circular conduit opening in oneapparatus element, while the opposing side of the gasket may beconstructed to sealingly engage a recessed flat surface surrounding acircular conduit opening in an opposing apparatus element.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the scope of theinvention. Accordingly, the foregoing description and drawings are byway of example only.

What is claimed is:
 1. A ring-shaped gasket for sealingly joiningopposed fluid conduit ports, the gasket comprising: a body having aradial outer surface, a first axial end surface, and a second axial endsurface, the body being pierced through by a hole creating a fluidpathway and defining a radial inner surface, at least one of the firstand second axial end surfaces having a stress concentration featureradially adjacent to a gasket sealing region, the gasket sealing regionbeing constructed and arranged to contact a face surface of acorresponding fluid conduit port.
 2. The gasket of claim 1, wherein thestress concentration feature is exterior to the fluid pathway defined bythe gasket sealing region.
 3. The gasket of claim 2, wherein the stressconcentration feature comprises a groove formed in the at least one ofthe first and second axial end surfaces.
 4. The gasket of claim 2,wherein the stress concentration feature comprises a groove formed inthe at least one of the first and second axial end surfaces, wherein awall of the groove closest the radial inner surface forms an acute anglewith a plane of the at least one of the first and second axial endsurfaces to form an undercut of the gasket sealing region.
 5. The gasketof claim 2, wherein the stress concentration feature comprises aU-shaped groove formed in the at least one of the first and second axialend surfaces, wherein substantially parallel walls of the groove form anacute angle with a plane of the at least one of the first and secondaxial end surfaces to form an undercut of the gasket sealing region. 6.The gasket of claim 2, wherein the stress concentration featurecomprises a groove formed in the at least one of the first and secondaxial end surfaces, wherein a wall of the groove closest the radialinner surface forms an acute angle with a plane of the at least one ofthe first and second axial end surfaces to form an undercut of thegasket sealing region, and wherein an outer periphery of the groove issurrounded by a portion of the at least one of the first and secondaxial end surfaces, the portion extending axially outward to a lesserextent than the gasket sealing region prior to installation of thegasket.
 7. The gasket of claim 2, wherein the stress concentrationfeature comprises a regular arrangement of cavities projecting into theat least one of the first and second axial end surfaces.
 8. The gasketof claim 2, wherein the stress concentration feature comprises aplurality of cavities projecting into the at least one of the first andsecond axial end surfaces, the plurality of cavities having individualvolumetric axes each forming an acute angle with a plane of the at leastone of the first and second axial end surfaces to form a plurality ofundercuts of the gasket sealing region.
 9. The gasket of claim 2,wherein the stress concentration feature comprises a plurality ofcavities projecting into the at least one of the first and second axialend surfaces, the plurality of cavities having individual volumetricaxes each forming an acute angle with a plane of the at least one of thefirst and second gasket axial end surfaces to form a plurality ofundercuts of the gasket sealing region, and wherein a circumferentialportion of the at least one of the first and second axial end surfacesradially adjacent the radial outer surface extends axially outward to alesser extent than the gasket sealing region prior to installation ofthe gasket.
 10. A ring-shaped gasket for sealingly joining opposed fluidconduit ports, the gasket comprising a body having a radial outersurface, a first axial end surface, and a second axial end surface, thebody being pierced through by a hole creating a fluid pathway anddefining a radial inner surface, wherein the first axial end surface hasa first stress concentration feature radially adjacent to a first gasketsealing region and exterior to the fluid pathway, the first gasketsealing region being constructed and arranged to contact a face surfaceof a first fluid conduit port, and wherein the second axial end surfacehas a second stress concentration feature radially adjacent to a secondgasket sealing region and exterior to the fluid pathway, the secondgasket sealing region being constructed and arranged to contact a facesurface of a second fluid conduit port.
 11. The gasket of claim 10,wherein the first stress concentration feature is substantiallyidentical to the second stress concentration feature.
 12. The gasket ofclaim 10, wherein the first stress concentration feature issubstantially different than the second stress concentration feature.13. The gasket of claim 10, wherein the first stress concentrationfeature is one of a groove and a plurality of cavities formed in thefirst axial end surface, and wherein the second stress concentrationfeature is the other of a groove and a plurality of cavities formed inthe second axial end surface.
 14. The gasket of claim 10, wherein thefirst stress concentration feature comprises a first plurality ofcavities formed in the first axial end surface, each cavity of the firstplurality of cavities having a volumetric axis forming an acute anglewith a plane of the first axial end surface to form a first plurality ofundercuts of the first gasket sealing region, and wherein the secondstress concentration feature comprises a second plurality of cavitiesformed in the second axial end surface, each cavity of the secondplurality of cavities having a volumetric axis forming an acute anglewith a plane of the second axial end surface to form a second pluralityof undercuts of the second gasket sealing region.
 15. The gasket ofclaim 14, wherein the volumetric axis of each respective cavity of thefirst plurality of cavities is disposed in an anti-phase relationshipwith the volumetric axis of a corresponding cavity of the secondplurality of cavities.
 16. The gasket of claim 10, wherein the firststress concentration feature comprises a first groove formed in thefirst axial end surface, a wall of the first groove closest the radialinner surface forming an acute angle with a plane of the first axial endsurface to form an undercut of the first gasket sealing region, andwherein the second stress concentration feature comprises a secondgroove formed in the second axial end surface, a wall of the secondgroove closest the radial inner surface forming an acute angle with aplane of the second axial end surface to form an undercut of the secondgasket sealing region.
 17. The gasket of claim 10, wherein the firststress concentration feature comprises a first U-shaped groove formed inthe first axial end surface, substantially parallel walls of the firstgroove forming an acute angle with a plane of the first axial endsurface to form an undercut of the first gasket sealing region, andwherein the second stress concentration feature comprises a second Ushaped groove formed in the second axial end surface, substantiallyparallel walls of the second groove forming an acute angle with a planeof the second axial end surface to form an undercut of the second gasketsealing region.
 18. The gasket of claim 17, wherein a circumferentialportion of the first axial end surface radially adjacent the radialouter surface extends axially outward to a lesser extent than the firstgasket sealing region prior to installation of the gasket, and wherein acircumferential portion of the second axial end surface radiallyadjacent the radial outer surface extends axially outward to a lesserextent than the second gasket sealing region prior to installation ofthe gasket.
 19. The gasket of claim 18, wherein the first gasket sealingregion and the second gasket sealing region each includes a sealingsurface having a greater radial extent of contact with the face surfaceof the first fluid conduit port and the second fluid conduit port,respectively, than can be achieved by plastic deformation of a sealhaving reduced contact areas to encourage plastic deformation.
 20. Aring-shaped gasket for sealingly joining opposed fluid conduit ports,the gasket comprising a body having a radial outer surface, a firstaxial end surface, and a second axial end surface, the body beingpierced through by a hole creating a fluid pathway and defining a radialinner surface, wherein the first axial end surface has a first stressconcentration feature radially adjacent to a first gasket sealingregion, the first gasket sealing region being constructed and arrangedto contact a face surface of a first fluid conduit port, and wherein thesecond axial end surface has an substantially flat second gasket sealingregion formed as a circumferential sector generally perpendicular withrespect to an axis of the hole and parallel to a plane of the secondaxial end surface prior to installation of the gasket. 21.-26.(canceled)